Seriously, what's the deal with Nitrogen?

I know the topic of nitrogen is something of a dead horse, but I'm at wit's end here trying to resolve feeding issues. I'm shipping packaged nitrogen to my cooling unit facility by train. I then have three lanes of unpackagers, each which should, in theory, produce 600 nitrogen gas / min. Each of these lanes then feed into four blenders, which should (in theory) be using exactly 600 nitrogen gas in total. This pipeline isn't long, there really isn't any slack at all between the unpackagers and the blenders, and I don't have any fluid buffers.

And yet for some reason, nitrogen gas isn't fully reaching the final blender (or in some cases final two blenders) in each line, leading to suboptimal efficiency. If I go look at the unpackagers, there is nitrogen gas actively building up inside them, despite them being hooked up to a MK2 pipeline that isn't even running at full speed (When I check it it's usually around 585 or 590). The three lanes are entirely independent, and all three seem to be having the exact same problem, so I'd assume if I figure out how to fix one of these it'll fix all three.

Has anyone run across this same issue? It seems really weird to me that gas is building up in the unpackager, when there's clearly headroom available in the pipe. I don't know if I'm missing something here, or if this is some kind of bug, but near as I can tell, the system *should* work.